With recent improvements in the performance of drive units, the volume of data storable in a single reel of a storage medium and the speed of data transfer by a drive unit have been dramatically increased. Accordingly, a tape library apparatus provided in a single casing has become the mainstream. Therefore, storage mediums, drive units, and so forth to be stored in a single casing are desired to be arranged at a high density.
FIG. 1 is an explanatory diagram of a conventional library apparatus. As illustrated in FIG. 1, a library apparatus 100 includes a casing 105. The casing 105 houses assemblies (hereinafter referred to as storage shelves) 102 of shelves (hereinafter referred to as cells) in which storage mediums 101 are stored, drive units 103, each of which performs the recording and reproduction of data into and from a storage medium 101, and a robot 104 that conveys the storage medium 101. The storage shelves 102 are provided on the right and left sides, respectively, of the library apparatus 100 when seen from the front in the direction A. The drive unit 103 is provided at the rear of the library apparatus 100 when seen from the front in the direction A. The robot 104 is provided in a central portion of the library apparatus 100. Such an arrangement is employed in a known method of densely arranging a plurality of reels of the storage mediums 101 and the drive units 103. In this arrangement, the robot 104 has a rotating mechanism so as to be accessible to the storage shelves 102 and the drive units 103 provided in three directions with respect thereto. The robot 104 also has mechanisms realizing vertical and horizontal movements thereof so as to be accessible to the drive units 103 and the storage shelves 102. Another exemplary technique is disclosed in Japanese Laid-open Patent Publication No. 2004-178702.
FIGS. 2A and 2B are other explanatory diagrams of the conventional known library apparatus 100. FIG. 2A is a top view of the library apparatus 100. As illustrated in FIG. 2A, the drive units 103 is oriented such that the depth direction thereof corresponds to the longitudinal direction of the casing 105 so that a storage medium insertion slot thereof faces the robot 104. The library apparatus 100 has dimensional restrictions on the width and depth thereof. Therefore, in a case where the storage shelves 102 are provided in a space avoiding a space in which the drive units 103, which has a large depth, is provided, the widths of the storage shelves 102 are limited. In such an arrangement, the efficiency in providing a sufficient capacity of the storage shelves 102 for storing the storage mediums 101 is reduced.
Referring now to FIG. 2B, the robot 104 has a rotating mechanism 106 so that the robot 104 can be oriented in any directions for access to the storage shelves 102 and the drive units 103. Therefore, a corresponding space extending in the height direction needs to be provided. Consequently, the storage shelves 102 need to be raised by a certain length from the bottom surface of the library apparatus 100. This further reduces the efficiency in providing a sufficient capacity of the storage shelves 102 for storing the storage mediums 101.